Container lid comprising metal body and synthetic resin liner

ABSTRACT

A container lid comprising a body made of a thin metal plate, the body having a top panel wall, and a skirt wall extending downwardly from the peripheral edge of the top panel wall; and a synthetic resin liner disposed on the inner surface of the top panel wall of the body, the liner being composed of a first layer ( 26 ) formed on the inner surface of the top panel wall; and a second layer ( 28 ) formed on the lower surface of the first layer. The thickness of a radially inner region of an outer peripheral edge portion ( 32 ) of the first layer is rendered larger than the thickness of a radially outer region of a central portion ( 30 ) of the first layer to make a step present at the boundary between the central portion and the outer peripheral edge portion. A toroidal thickness varying region ( 34 ) whose thickness gradually decreases radially outwardly is made present in the central portion of the first layer.

TECHNICAL FIELD

This invention relates to a container lid comprising a body made of a thin metal plate, the body having a circular top panel wall, and a cylindrical skirt wall extending downwardly from the peripheral edge of the top panel wall; and a synthetic resin liner disposed on the inner surface of the top panel wall of the body.

BACKGROUND ART

Containers, generally called bottle cans or metal bottles, are formed from thin metal plates such as aluminum-based alloys. In each of such containers, an outward curl is formed in an upper end part of a cylindrical mouth-neck section, and an internal thread and a locking jaw located below it are formed on the outer peripheral surface of the mouth-neck section. As container lids particularly suitable for such containers, Patent Documents 1 and 2 shown below disclose container lids each comprising a body made of a thin metal plate, the body having a circular top panel wall, and a cylindrical skirt wall extending downwardly from the peripheral edge of the top panel wall; and a synthetic resin liner disposed on the inner surface of the top panel wall of the body. An annular concavity is formed in an upper end part of the skirt wall of the body. The liner is composed of a first layer formed by press-molding a rigid synthetic resin material supplied to the inner surface of the top panel wall, and a second layer formed by press-molding a flexible synthetic resin material supplied to the lower surface of the first layer. The first layer of the liner has a circular central portion extending along the inner surface of the top panel wall of the body, and a toroidal outer peripheral edge portion extending along an outer peripheral edge part of the top panel wall of the body and along the upper end part of the skirt wall. The second layer of the liner is laminated to the central portion of the first layer.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP-A-2015-3325

Patent Document 2: JP-A-2016-26961

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

According to the present inventors' experiences, the conventional container lid of the above-described form has been found to pose the following problems to be solved: (1) When the second layer is press-molded, it is highly likely that a radially inner region in the outer peripheral edge portion of the first layer, namely a part in the outer peripheral edge portion which is adjacent to the central portion, will be damaged. (2) When the second layer is to be press-molded, the synthetic resin for forming the second layer fails to flow sufficiently smoothly and as required, so that the second layer of a required shape may fail to be press-molded.

The present invention has been accomplished in the light of the above facts. Its first challenge is to provide a novel and improved container lid which is maximally freed from a situation where the radially inner region in the outer peripheral edge portion of the first layer is damaged when the second layer is press-molded, without other problems, such as a considerable increase in the consumption of the material used, being raised.

A second challenge facing the present invention is to provide a novel and improved container lid in which the second layer of the required shape can be press-molded reliably.

Means for Solving the Problems

Upon in-depth studies and experiments, the present inventors have recognized the following cause of the situation where the radially inner region of the outer peripheral edge portion of the first layer is damaged when the second layer is press-molded: The thickness of the radially inner region of the outer peripheral edge portion, which should normally be the same as the thickness of a radially outer region of the central portion adjacent thereto, is actually too small. Thus, the radially inner region of the outer peripheral edge portion of the first layer does not have sufficient resistance against contact under a considerable pressing force exerted by a mold component for press-molding the second layer. In recognition of this cause, the inventors have found that the first challenge can be solved by making the thickness of the radially inner region of the outer peripheral edge portion of the first layer larger than the thickness of the radially outer region of the central portion to render a step existent at a boundary between the central portion and the outer peripheral edge portion (the first challenge can also be solved even if no step is made present by similarly increasing the thickness the radially outer region of the central portion; this measure, however, will increase the amount of the material necessary for formation of the first layer).

Moreover, the present inventors have found, upon in-depth studies and experiments, that when a toroidal thickness varying region whose thickness gradually decreases radially outwardly is rendered present in the central portion of the first layer, the synthetic resin material for forming the second layer can be flowed sufficiently smoothly during press molding of the second layer.

That is, according to the present invention, there is provided, as a container lid for solving the above first challenge, a container lid comprising a body made of a thin metal plate, the body having a circular top panel wall, and a cylindrical skirt wall extending downwardly from the peripheral edge of the top panel wall; and a synthetic resin liner disposed on the inner surface of the top panel wall of the body,

the liner being composed of a first layer formed by press-molding a rigid synthetic resin material supplied to the inner surface of the top panel wall, and a second layer formed by press-molding a flexible synthetic resin material supplied to the lower surface of the first layer,

the first layer of the liner having a circular central portion extending along the inner surface of the top panel wall of the body; and a toroidal outer peripheral edge portion extending along the inner surface of an outer peripheral edge part of the top panel wall of the body and along the inner surface of an upper end part of the skirt wall, and

the second layer of the liner being laminated to the central portion of the first layer,

wherein the wall thickness of a radially inner region of the outer peripheral edge portion of the first layer of the liner is larger than the wall thickness of a radially outer region of the central portion of the first layer, and a step is present at a boundary between the central portion and the outer peripheral edge portion.

According to the present invention, moreover, there is provided, as a container lid for solving the above second challenge, a container lid comprising a body made of a thin metal plate, the body having a circular top panel wall, and a cylindrical skirt wall extending downwardly from the peripheral edge of the top panel wall; and a synthetic resin liner disposed on the inner surface of the top panel wall of the body,

the liner being composed of a first layer formed by press-molding a rigid synthetic resin material supplied to the inner surface of the top panel wall; and a second layer formed by press-molding a flexible synthetic resin material supplied to the lower surface of the first layer,

the first layer of the liner having a circular central portion extending along the inner surface of the top panel wall of the body; and a toroidal outer peripheral edge portion extending along the inner surface of an outer peripheral edge part of the top panel wall of the body and along the inner surface of an upper end part of the skirt wall, and

the second layer of the liner being laminated to the central portion of the first layer,

wherein a toroidal thickness varying region whose thickness gradually decreases radially outwardly is present in the central portion of the first layer.

The step preferably measures 0.05 to 0.40 mm. Preferably, the second layer has a circular thin-walled central portion, and a toroidal thick-walled outer peripheral edge portion; an annular protrusion protruding downward is present in a radially inner region of the thick-walled outer peripheral edge portion; and the outer peripheral edge of the thickness varying region of the first layer is located radially inwardly of the inner peripheral edge of the annular protrusion. Advantageously, the thickness varying region of the first layer is located opposite a radially outer region of the thin-walled central portion of the second layer; and the thickness of the radially outer region of the thin-walled central portion of the second layer gradually increases radially outwardly in accordance with thickness variations of the thickness varying region of the first layer. The thickness varying region desirably inclines at an inclination angle of 0.5 to 3.0 degrees relative to the horizontal. Advantageously, the container lid is applied to a container made of a thin metal plate, the container having an outward curl formed at the leading end of a mouth-neck section thereof, an outer peripheral surface of the annular protrusion of the second layer of the liner is brought into intimate contact with an upper end part of the inner peripheral surface of the outward curl; and a lower surface of a radially outer region of the thick-walled outer peripheral edge portion located radially outwardly of the annular projection is brought into intimate contact with an upper surface to an outer peripheral surface of the outward curl.

The terms “upper” and “lower” used herein and in the “Claims” refer, respectively, to the upper and lower positions in the upright state of the container lid (namely, each of the states illustrated in FIGS. 1 to 3).

Effects of the Invention

In the container lid of the present invention, the wall thickness of the radially inner region of the outer peripheral edge portion of the first layer of the liner is larger than the wall thickness of the radially outer region of the central portion, and the step is present at the boundary between the central portion and the outer peripheral edge portion. In such a container lid, the wall thickness of the radially inner region of the outer peripheral edge portion of the first layer of the liner can be rendered a sufficient thickness, without an excessive increase in the amount of the material necessary for molding of the first layer. Thus, a situation where the radially inner region in the outer peripheral edge portion of the first layer is damaged during the press molding of the second layer can be avoided as much as possible.

In the container lid of the present invention, moreover, the toroidal thickness varying region whose thickness gradually decreases radially outwardly is present in the central portion of the first layer. In such a container lid, the flow of the material during press molding of the second layer is promoted owing to the presence of the thickness varying region. Thus, the second layer of the required shape can be press-molded reliably.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view, partly in cross section, showing a preferred embodiment of a container lid configured in accordance with the present invention.

FIG. 2 is an enlarged view showing a part of FIG. 1 on an enlarged scale.

FIG. 3 is a front view, partly in cross section, showing a state in which the container lid shown in FIG. 1 is mounted on a mouth-neck section of a container made of a thin plate to seal the mouth-neck section.

FIG. 4 is an enlarged view showing a part of FIG. 3 on an enlarged scale.

MODE FOR CARRYING OUT THE INVENTION

The present invention will now be described in further detail by reference to the accompanying drawings illustrating a preferred embodiment of a container lid configured in accordance with the present invention.

With reference to FIG. 1, a container lid entirely indicated at 2, which has been configured in accordance with the present invention, comprises a body 4 made of a thin metal plate and a liner 6 made of a synthetic resin.

The body 4, which can be formed from a suitable thin metal plate such as a thin plate of an aluminum-based alloy, has a circular top panel wall 8, and a cylindrical skirt wall 10 extending downwardly from the peripheral edge of the top panel wall 8. A boundary region between the top panel wall 8 and the skirt wall 10 is in an arcuate shape as viewed in a cross section. An annular concavity 12 continuously extending in a circumferential direction is formed in an upper end part of the skirt wall 10. In a region directly below the annular concavity 12, a plurality of slits (notches) 14 extending in the circumferential direction are formed at intervals in the circumferential direction. Regions located below the slits 14 are displaced radially inwardly. In a lower end part of the skirt wall 10, a circumferential breakable line 16 is disposed, whereby the skirt wall 10 is divided into a main portion 18 located above the circumferential breakable line 16, and a tamper-evident bottom portion 20 located below the circumferential breakable line 16. The circumferential breakable line 16 in the illustrated embodiment is composed of a plurality of slits 22 extending in the circumferential direction at intervals in the circumferential direction, and a plurality of bridge portions 24 left between these slits 22. The tamper-evident bottom portion 20 is connected to the main portion 18 via the plurality of bridge portions 24. Such a body 4 itself is in a well-known configuration, and thus a detailed explanation for the body 4 is omitted herein.

With further reference to FIG. 2 along with FIG. 1, the liner 6 is composed of a first layer 26 and a second layer 28. The first layer 26 is formed by press-molding a synthetic resin material supplied to the inner surface of the top panel wall 8 of the body 4. More detailedly, the body 4 is held in an inverted state on a rest (not shown), a synthetic resin material in a softened molten state is supplied to the middle of the top panel wall 8, and a press-molding member (not shown) of a required shape is pressed against the synthetic resin material at a required pressure, whereby the first layer 26 is formed. It is important that the first layer 26 be molded from a rigid synthetic resin excellent in gas barrier properties, such as polyethylene or polypropylene. However, the first layer 26 is higher in gas barrier properties than the second layer 28 constituting a sealing layer. The second layer 28 is formed by press-molding a synthetic resin material supplied to the lower surface of the first layer 26. More detailedly, the body 4 having the first layer 26 formed therein is held in an inverted state on the rest (not shown), a synthetic resin material in a softened molten state is supplied to the middle of the first layer 26, and a press-molding member (not shown) of a required shape is pressed against the synthetic resin material at a required pressure, whereby the second layer 28 is formed. It is important that the second layer 28 be molded from a flexible synthetic resin excellent in sealing properties, such as polyethylene or elastomer.

The first layer 26 has a circular central portion 30 extending along the inner surface of the top panel wall 8 of the body 4, and a toroidal outer peripheral edge portion 32 extending along the inner surface of an outer peripheral edge part of the top panel wall 8 of the body 4 and along the inner surface of an upper end part of the skirt wall 10. It is important that a toroidal thickness varying region 34 whose thickness gradually decreases radially outwardly (accordingly, its lower surface extends in an upwardly inclined manner toward the outside in the radial direction) be present in the central portion 30 (the outer peripheral edge of the thickness varying region 34 is preferably situated near an annular protrusion 40 (to be described later) of the second layer 28 and radially inwardly thereof). The inclination angle α of the lower surface of the thickness varying region 34 relative to the horizontal is preferably 0.5 to 3.0 degrees. The wall thickness of a radially inner region of the outer peripheral edge portion 32 of the first layer 26 is larger than the wall thickness of a radially outer region of the central portion 30, and a step s, which preferably has a dimension of the order of 0.05 to 0.40 mm, is present at a boundary between the central portion 30 and the outer peripheral edge portion 32.

The second layer 28 laminated to the central portion 30 of the first layer 26 has a circular thin-walled central portion 36, and a toroidal thick-walled outer peripheral edge portion 38. In a radially inner region of the outer peripheral edge portion 38, the annular protrusion 40 protruding downward is present.

In the container lid 2 configured in accordance with the present invention, the wall thickness of the radially inner region of the outer peripheral edge portion 32 of the first layer 26 constituting the liner 6 is larger than the wall thickness of the radially outer region of the central portion 30, and the step s is present at the boundary between the central portion 30 and the outer peripheral edge portion 32. In other words, the wall thickness of the radially inner region of the outer peripheral edge portion 32 of the first layer 26 is relatively large. Hence, although the press-molding member acts on the radially inner region of the outer peripheral edge portion 32 of the first layer 26 during molding of the second layer 28, 0.5 damage to the outer peripheral edge portion 32 of the first layer 26 potentially caused by this action is avoided as much as possible. The wall thickness of the radially outer region of the central portion 30 of the first layer 26 is relatively small, so that the amount of the synthetic resin material for forming the first layer 26 does not excessively increase. In the container lid 2 configured in accordance with the present invention, moreover, the thickness varying region 34 whose thickness gradually decreases radially outwardly is present in the central portion 30 of the first layer 26. When the second layer 28 is to be press-molded, therefore, the synthetic resin material flows sufficiently smoothly to the outside in the radial direction, with the result that the second layer 28 of the required shape can be formed sufficiently reliably.

FIGS. 3 and 4 show a mouth-neck section 42 of a container to which the container lid 2 is applied. The mouth-neck section 42 of the container of a shape well known per se, which can be formed from a suitable thin metal plate such as a chromated thin steel plate, a thin tinplate, or a thin plate of an aluminum-based alloy, is in a nearly cylindrical shape as a whole, and has an outward curl 44 formed in an upper end part whose outer diameter gradually decreases upwardly. An external thread 46 and a locking jaw 48 located below the external thread 46 are formed in an outer peripheral surface of a main part of the mouth-neck section 42.

In mounting the container lid 2 on the mouth-neck section 42 of the container to seal the mouth-neck section 42, the container lid 2 is fitted onto the mouth-neck section 42, and pressed downward to create a state in which the second layer 28 of the liner 6 is brought into intimate contact with the top of the mouth-neck section 42, more detailedly, a state in which the outer peripheral surface of the annular protrusion 40 of the second layer 28 and the lower surface of the radially outer region of the thick-walled outer peripheral edge portion 38 located radially outwardly of the annular protrusion 40 are brought into intimate contact with the upper end of the inner peripheral surface to the upper surface of the outward curl 44 of the mouth-neck section 42. With this state being maintained, the outer peripheral edge part of the top panel wall 8 and the upper end part of the skirt wall 10 in the body 4 are deformed into a shape as illustrated in FIGS. 3 and 4. As a result, the outer peripheral surface of the annular protrusion 40 of the second layer 28 of the liner 6 is brought into intimate contact with the upper end part of the inner peripheral surface of the outward curl 44, and the lower surface of the radially outer region of the thick-walled outer peripheral edge portion 38 located radially outwardly of the annular protrusion 40 is brought into intimate contact with the upper surface to the outer peripheral surface of the outward curl 44. Furthermore, the main portion 18 of the skirt wall 10 of the body 4 is deformed along the external thread 46 formed in the mouth-neck section 42 of the container to form an internal thread, while a lower end part of the tamper-evident bottom portion 20 in the skirt wall 10 of the body 4 is deformed radially inwardly and locked to the locking jaw 48 in the mouth-neck section 42 of the container.

In unsealing the mouth-neck section 42 in order to consume the contents of the container, the fingers are hooked onto the skirt wall 8 of the body 4 to rotate the container lid 2 in an opening direction, namely, in a counterclockwise direction as viewed from above in FIG. 3. By so doing, the internal thread formed in the main portion 18 of the skirt wall 10 is moved along the external thread 46 of the mouth-neck section 42, whereupon the container lid 2 is moved upward relative to the mouth-neck section 42. On the other hand, the tamper-evident bottom portion 20 of the skirt wall 10, whose lower end part has been locked to the locking jaw 48 of the mouth-neck section 42, is inhibited from moving upward. Consequently, stress is generated in the bridge portions 24 in the circumferential breakable line 16 formed in the skirt wall 10, whereby the bridge portions 24 are broken. Afterwards, the container lid 2 is moved upward in accordance with its rotations, with the tamper-evident bottom portion 20 being left behind, until it is removed from the mouth-neck section 42. In this manner, the mouth-neck section 42 is unsealed.

EXPLANATIONS OF LETTERS OR NUMERALS

-   -   2: Container lid     -   4: Body     -   6: Liner     -   8: Top panel wall     -   10: Skirt wall     -   26: First layer     -   28: Second layer     -   30: Central portion of first layer     -   32: Outer peripheral edge portion of first layer     -   34: Thickness varying region     -   36: Thin-walled central portion of second layer     -   38: Thick-walled outer peripheral edge portion of second layer     -   40: Annular protrusion     -   42: Mouth-neck section of container 

1. A container lid comprising a body made of a thin metal plate, the body having a circular top panel wall, and a cylindrical skirt wall extending downwardly from a peripheral edge of the top panel wall; and a synthetic resin liner disposed on an inner surface of the top panel wall of the body, the liner being composed of a first layer formed by press-molding a rigid synthetic resin material supplied to the inner surface of the top panel wall; and a second layer formed by press-molding a flexible synthetic resin material supplied to a lower surface of the first layer, the first layer of the liner having a circular central portion extending along the inner surface of the top panel wall of the body; and a toroidal outer peripheral edge portion extending along an inner surface of an outer peripheral edge part of the top panel wall of the body and along an inner surface of an upper end part of the skirt wall, and the second layer of the liner being laminated to the central portion of the first layer, wherein a wall thickness of a radially inner region of the outer peripheral edge portion of the first layer of the liner is larger than a wall thickness of a radially outer region of the central portion of the first layer, and a step is present at a boundary between the central portion and the outer peripheral edge portion.
 2. The container lid according to claim 1, wherein the step measures 0.05 to 0.40 mm.
 3. The container lid according to claim 1, wherein a toroidal thickness varying region whose thickness gradually decreases radially outwardly is present in the central portion of the first layer.
 4. The container lid according to claim 3, wherein the second layer has a circular thin-walled central portion, and a toroidal thick-walled outer peripheral edge portion; an annular protrusion protruding downward is present in a radially inner region of the thick-walled outer peripheral edge portion; and an outer peripheral edge of the thickness varying region of the first layer is located radially inwardly of an inner peripheral edge of the annular protrusion.
 5. The container lid according to claim 4, wherein the thickness varying region of the first layer is located opposite a radially outer region of the thin-walled central portion of the second layer; and a thickness of the radially outer region of the thin-walled central portion of the second layer gradually increases radially outwardly in accordance with thickness variations of the thickness varying region of the first layer.
 6. The container lid according to claim 3, wherein the thickness varying region inclines at an inclination angle of 0.5 to 3.0 degrees relative to a horizontal.
 7. The container lid according to claim 4, which is applied to a container made of a thin metal plate, the container having an outward curl formed at a leading end of a mouth-neck section thereof, wherein an outer peripheral surface of the annular protrusion of the second layer of the liner is brought into intimate contact with an upper end part of an inner peripheral surface of the outward curl; and a lower surface of a radially outer region of the thick-walled outer peripheral edge portion located radially outwardly of the annular projection is brought into intimate contact with an upper surface to an outer peripheral surface of the outward curl.
 8. A container lid comprising a body made of a thin metal plate, the body having a circular top panel wall, and a cylindrical skirt wall extending downwardly from a peripheral edge of the top panel wall; and a synthetic resin liner disposed on an inner surface of the top panel wall of the body, the liner being composed of a first layer formed by press-molding a rigid synthetic resin material supplied to the inner surface of the top panel wall; and a second layer formed by press-molding a flexible synthetic resin material supplied to a lower surface of the first layer, the first layer of the liner having a circular central portion extending along the inner surface of the top panel wall of the body; and a toroidal outer peripheral edge portion extending along an inner surface of an outer peripheral edge part of the top panel wall of the body and along an inner surface of an upper end part of the skirt wall, and the second layer of the liner being laminated to the central portion of the first layer, wherein a toroidal thickness varying region whose thickness gradually decreases radially outwardly is present in the central portion of the first layer.
 9. The container lid according to claim 8, wherein the second layer has a circular thin-walled central portion, and a toroidal thick-walled outer peripheral edge portion; an annular protrusion protruding downward is present in a radially inner region of the thick-walled outer peripheral edge portion; and an outer peripheral edge of the thickness varying region of the first layer is located radially inwardly of an inner peripheral edge of the annular protrusion.
 10. The container lid according to claim 9, wherein the thickness varying region of the first layer is located opposite a radially outer region of the thin-walled central portion of the second layer; and a thickness of the radially outer region of the thin-walled central portion of the second layer gradually increases radially outwardly in accordance with thickness variations of the thickness varying region of the first layer.
 11. The container lid according to claim 8, wherein the thickness varying region inclines at an inclination angle of 0.5 to 3.0 degrees relative to a horizontal.
 12. The container lid according to claim 8, which is applied to a container made of a thin metal plate, the container having an outward curl formed at a leading end of a mouth-neck section thereof, wherein an outer peripheral surface of the annular protrusion of the second layer of the liner is brought into intimate contact with an upper end part of an inner peripheral surface of the outward curl; and a lower surface of a radially outer region of the thick-walled outer peripheral edge portion located radially outwardly of the annular projection is brought into intimate contact with an upper surface to an outer peripheral surface of the outward curl. 